In solving this problem, $5 will be a fixed cost and $2.25 will be a variable cost, depending on the number of videos rented in a month. If you signify the number of videos rented in a month as V, and your total price per month as P, the algebraic expression
5+2.25V=P
will be a model of the relationship.
You will need to know how many videos you rented to solve the equation; however if the question is asking you for an algebraic representation this should be sufficient.
